Epidemic thunderstorm asthma events have the power both to induce asthma and to reactivate past asthma, with symptoms persisting three years later, experts say.
Researchers from Eastern Health and Monash University followed people affected by the event that struck Melbourne on 21 November, 2016, in what the authors say is the largest cohort and longest follow-up of these patients.
It was the most catastrophic thunderstorm asthma event in the world, triggering more than 3,500 emergency department presentations and resulting in 10 deaths.
Study participants had presented to the emergency department of Eastern Health and were contacted with a questionnaire in December 2016. Participants who agreed to the follow-up study then completed phone questionnaires 12, 24, and 36 months later, with 208, 164, and 112 respondents in each respective year.
“Specific questions regarding frequency of asthma symptoms, use of inhaled preventer, asthma action plan ownership, and need for urgent healthcare utilization in the preceding 12 months were included,” the paper says.
The authors found that 70-85% of respondents reported ongoing asthma symptoms in any given year, and up to 28% experienced them weekly.
The cohort was also divided based on 2016 asthma status: those with any previous diagnosis by a doctor labelled as “current asthma” (those with symptoms in the 12 months before November 2016) and “past asthma” (no symptoms in the previous year); “possible undiagnosed asthma” based on symptoms suggestive of the condition that either disrupted sleep or occurred with colds, hayfever or exercise; and “no asthma”.
“Notably, 92% (n = 12) of those who had reported ‘past asthma’, that is no asthma symptoms in the 12 months preceding the 2016 ETSA event, reported asthma symptoms on 12-month follow-up,” the authors wrote in Asia Pacific Allergy.
Among the 64 people with no previous diagnosis of asthma before November 2016, 35 had possible undiagnosed asthma and 29 had no asthma.
“At 36-month follow-up, 69% of respondents with ‘no asthma’ remained symptomatic with 14% experiencing persistent symptoms [at least once per week],” the paper said.
Of those with “possible” but undiagnosed asthma before 2016, about 80% reported asthma symptoms in any given year during follow-up.
Lead author Professor Francis Thien told Allergy & Respiratory Republic the apparent reactivation and induction of asthma were particularly important.
“All groups showed that after November they were more symptomatic than they were before,” said Professor Thien, who is director of respiratory medicine at Eastern Health.
“But one of the things that was striking was a significant proportion of the people who said that they’ve never had asthma before 2016 then said that they’ve had persistent asthma, suggesting that [the thunderstorm] induced persistent asthma in a proportion of patients.
“Secondly, the people who said that they had asthma in the past but it had resolved and they didn’t have symptoms in the last year, a significant proportion of them also had persistent asthma, suggesting it reactivated their asthma.”
Less than 40% of respondents had an asthma action plan, and while 50% of the cohort reported being prescribed inhaled corticosteroid preventers only 40-50% of them were adherent at least five days per week.
These low rates of asthma action plan ownership and inhaler adherence may contribute to increased morbidity and mortality in future such events, the authors said.
“I think that’s an opportunity for improvement,” Professor Thien said.
He noted there were several issues with their asthma control, including low engagement in healthcare among young adults.
“Even trying to get them to come back for follow-up appointments is challenging – [most participants were] in their early 30s so they’re usually working young adults and getting them to then see a doctor or be adherent with asthma treatment has been challenging.”
The authors said limitations of the study included a small sample size and no control group of people with a similar demographic profile but who were unaffected by the 2016 event.
However, Professor Thien said the work underscored the importance of “identification of risk factors such as allergic rhinitis and pollen sensitisation, with patient education on preventer adherence and asthma action plans.
“The role of increasing atmospheric carbon dioxide concentrations and temperatures may increase aeroallergen levels. Climate change may extend pollen seasons worldwide, with increasing likelihood of extreme weather events such as thunderstorms and may increase the risk of more frequent epidemic thunderstorm asthma events in the future.”
Updated guidance to primary practitioners on managing thunderstorm asthma is provided in the Australian Asthma Handbook, which was launched this week (register here for the launch webinar on 1 September).
Recommendations include that for people with asthma at risk of thunderstorm asthma, practitioners should:
- prescribe inhaled corticosteroid-containing treatment as the person’s usual asthma treatment to reduce the risk of severe flare-ups.
- If a patient has few asthma symptoms and is not already using an inhaled corticosteroids-containing preventer, start inhaled corticosteroid treatment (low-dose inhaled corticosteroid plus as-needed SABA, or as-needed low-dose budesonide–formoterol) at least 2 weeks before and the pollen season and explain they need to keep taking it at least throughout the pollen season (e.g. in Victoria, ideally 1 September–31 December – refer to pollen calendars for information on high-risk periods in other regions)
- provide training in correct inhaler technique, and check technique and adherence regularly
- advise patients to carry a reliever inhaler (short-acting beta2 agonist or inhaled corticosteroid–formoterol, according to their prescribed treatment regimen) and replace it before the expiry date (e.g. keep a spare)
- provide an up-to-date written asthma action plan that includes thunderstorm advice and instructs the person to increase doses of both inhaled preventer and reliever (as well as starting oral corticosteroids, if indicated) in response to flare-ups.